Influence of Tool Posture and Position on Stability in Milling with Parallel Kinematic Machine Tool
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International Journal of Precision Engineering and Manufacturing https://doi.org/10.1007/s12541-020-00416-7
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Influence of Tool Posture and Position on Stability in Milling with Parallel Kinematic Machine Tool Muizuddin Azka1,2 · Keiji Yamada1 · Mahfudz Al Huda2 · Ryutaro Tanaka1 · Katsuhiko Sekiya1 Received: 24 March 2020 / Revised: 3 September 2020 / Accepted: 13 September 2020 © Korean Society for Precision Engineering 2020
Abstract This paper investigated the machining stability influenced by tool posture and position in ball-end milling with parallel kinematic machine tool (PKM). Initially, the geometric structure was identified, and the machinery stiffness was measured by impulse respond method at several positions with four tool postures. Then, the milling tests were conducted on flat work surface using a ball-end mills. Cutting force and acceleration signals of milling tests were measured by three-axis dynamometer and accelerometer. Furthermore, these signals were analyzed by using Fast-Fourier transform and Hilbert–Huang transform (HHT). The results showed that the length of arm change with tool posture, where the machinery stiffness decreased with the total length of arms for any tool position. The experimental results also demonstrated the machining stability varied with tool posture; the trend of stability corresponds with the machinery stiffness. The vibration analysis by HHT presented the increasing of power level in the time–frequency plot when the length of arm increase during milling process. Therefore, the geometric influence must be considered to support process planning on the PKM. Keywords Tool posture and position · Ball-end milling · Parallel kinematic machine tool · Machinery stiffness · Machining stability · Hilbert–Huang transform List of Symbols a Depth of slot (mm) AX Acceleration signal in X-direction (m/s2) AY Acceleration signal in Y-direction (m/s2) AZ Acceleration signal in Z-direction (m/s2) n Spindle rotation (min−1) fn Natural frequency (Hz) fT Tooth-passing frequency (Hz) fc Self-excited chatter frequency (Hz) FX Force signal in X-direction (N) FY Force signal in Y-direction (N) FZ Force signal in Z-direction (N) G Dynamic compliance (µm/N) K Machinery stiffness (MN/m) Nt Number of flutes VX Feeding speed in X-direction (mm/min) * Keiji Yamada keiji@hiroshima‑u.ac.jp 1
Graduate School of Engineering, Hiroshima University, 1‑4‑1 Kagamiyama, Higashi‑Hiroshima, Hiroshima 739‑8527, Japan
Agency for the Assessment and Application of Technology (BPPT), Jakarta 10340, Indonesia
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VY Feeding speed in Y-direction (mm/min) X Machine coordinate system in X-axis (mm) Y Machine coordinate system in Y-axis (mm) Z Machine coordinate system in Z-axis (mm) θA Tool posture in A-axis (°) θB Tool posture in B-axis (°)
1 Introduction A lot of mechanical parts contain complexed surfaces which are finished by ball-end of milling tool traveling along a desired cutting path. The tool axis is generally inclined against the machined surface for preventing
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